Autoscrubber convertible between manual and autonomous operation

ABSTRACT

Autoscrubbers are capable of being operated in a manual (e.g. walk-behind) mode and an autonomous (operator free) mode and capable of switching between such operational modes. Apparatus and methods for steering such autoscrubbers use steering torque mechanisms to apply steering torques independently to left and right drive wheels. Steering systems for autonomous operation may be retrofit onto existing walk-behind autoscrubbers to implement this functionality. The autonomous control capability may not detract appreciably from an operator&#39;s ability to use the autoscrubber in a manual (walk-behind) mode.

RELATED APPLICATIONS

This application is a continuation of PCT international application No.PCT/CA2017/050430 which has an international filing date of 7 Apr. 2017and claims priority from U.S. application No. 62/320,294 filed on 8 Apr.2016. PCT application No. PCT/CA2017/050430 and U.S. application No.62/320,294 are both hereby incorporated herein by reference.

TECHNICAL FIELD

The technology disclosed herein relates to the field of cleaning floors.Particular embodiments provide floor-cleaning apparatus (floorscrubbers) convertible between a manually controlled operational modeand an autonomous operational mode.

BACKGROUND

A conventional floor scrubbing machine is commonly known within thecleaning industry as an “autoscrubber”. Common autoscrubbers (known aswalk behind autoscrubbers) include handlebars or the like which aregripped by a user to control the movement of the autoscrubber. Prior artautoscrubbers are self-propelled by a single motor coupled to atransaxle which serves as a speed reducer (transmission) for the motorand also as a differential to split torque between the two drive wheels.A user controls the speed of the motor (and the corresponding speed ofthe autoscrubber) via a suitable control input (e.g. a knob, a slider,or some other suitable form of hand-operated throttle controlmechanism). Cleaning functions and other parameters of prior artautoscrubbers (e.g. speed of brush, rate of soap dispensing) aretypically set manually by the operator or are configured to operate incorrelation to the drive speed. To steer the autoscrubber, the operatorphysically turns and guides the apparatus by hand by asserting force onthe handlebar. Typical prior art autoscrubbers do not include anycontrollable inputs for facilitating steering by application ofdifferent torques to the different drive wheels. Instead, turning suchprior art autoscrubbers requires the application of significant force bythe user.

There is a general desire to reduce the human user involvement in theoperation of autoscrubbers.

There is a desire, in some situations, to provide autoscrubbers thatprovide autonomous autoscrubbing functionality.

There is a desire, in some situations, to retrofit conventional(manually operated) autoscrubbers to permit autonomous autoscrubbingfunctionality.

While autonomous operation of an autoscrubber can be advantageous insome circumstances, there are some circumstances (e.g. when there areparticular regions of the floor being cleaned that require extraattention, where there are particular regions of the floor being cleanedthat are spatially confined, where there are other humans present on thefloor being cleaned, where the regions of the floor being cleaned changerapidly and/or the like) where it can be desirable to facilitate manualoperation of the autoscrubbing device or to switch between autonomousautoscrubbing functionality and manual operation of the autoscrubber. Insome circumstances, there is a desire that such manual operation be asclose as possible (in terms of user experience) to the operation ofconventional (i.e. manually operated) autoscrubbers.

The foregoing examples of the related art and limitations relatedthereto are intended to be illustrative and not exclusive. Otherlimitations of the related art will become apparent to those of skill inthe art upon a reading of the specification and a study of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in referenced figures of thedrawings. It is intended that the embodiments and figures disclosedherein are to be considered illustrative rather than restrictive.

FIG. 1A is a schematic depiction of a steering system for anautoscrubber convertible between a manually controlled operational modeand an autonomous operational mode according to a particular embodiment.FIG. 1B is a schematic depiction of an example embodiment of the FIG. 1Aautoscrubber and steering system. FIG. 1C is a schematic depiction ofanother example embodiment of the FIG. 1A autoscrubber and steeringsystem. FIGS. 1A, 1B and 1C may be referred to collectively herein asFIG. 1.

FIG. 2A is a schematic depiction of a number of components of the FIG.1A autoscrubber with the FIG. 1B steering system in autonomousoperational mode. FIG. 2B is a schematic depiction of a number ofcomponents of the FIG. 1A autoscrubber with the FIG. 1B steering systemin a manual operational mode. FIG. 2C is a schematic depiction of anumber of components of the FIG. 1A autoscrubber with the FIG. 1Csteering system in autonomous operational mode. FIG. 2D is a schematicdepiction of a number of components of the FIG. 1A autoscrubber with theFIG. 1C steering system in a manual operational mode. FIG. 2E is aschematic depiction of a method for implementing feedforwardfreewheeling control.

FIG. 3 is a state machine representation of a localization andnavigation system (LNS) suitable for use with the FIG. 1 autoscrubberoperating in teach and repeat modes according to a particularembodiment. FIG. 3B depicts a state machine representation of alocalization and navigation system (LNS) suitable for use with the FIG.1 autoscrubber in a repeat mode according to another particularembodiment.

FIG. 4 is a schematic depiction of a software architecture of a LNSsuitable for use with the FIG. 1 autoscrubber according to a particularembodiment. FIG. 4B depicts a software architecture of a LNS suitablefor use with the FIG. 1 autoscrubber according to another particularembodiment.

FIG. 5 is a schematic depiction of a path on which a user can guide theFIG. 1 autoscrubber in a first run and the FIG. 1 autoscrubber canimplement autonomously in second and subsequent runs.

FIGS. 6A-6D (collectively, FIG. 6) are schematic depictions of imagedata captured by the camera of the FIG. 1 autoscrubber and how suchimage data can be compared to saved feature data to guide theautoscrubber during autonomous operation according to a particularembodiment.

FIG. 7 is a schematic illustration of an autoscrubber according to aparticular embodiment, which may comprise a walk-behind autoscrubberretrofitted to provide both a manual (e.g. walk-behind) operational modeand autonomous (operator free) operation mode or a new constructionautoscrubber capable of operating in manual (e.g. walk-behind)operational mode and autonomous (operator free) operation mode. The FIG.1 steering system (or components thereof) may be incorporated into FIG.7 autoscrubber.

FIG. 8 is a schematic illustration of a remote monitoring system, whichmay be used in connection with the FIG. 1 autoscrubber according to aparticular embodiment.

FIGS. 9A and 9B schematically illustrate one technique which may be usedfor deciding when to start tracking reference observations from the nextnode in a selected path according to a particular embodiment.

FIG. 10 is block diagram representation of a feedback controlsystem/algorithm suitable for controlling the FIG. 1C steering system ofthe FIG. 1 autoscrubber in autonomous mode according to a particularembodiment.

FIG. 11 is a block diagram representation of a MIMO controlsystem/algorithm suitable for controlling the FIG. 1C steering system ofthe FIG. 1 autoscrubber in autonomous mode according to anotherparticular embodiment.

FIG. 12 is a block diagram representation of an autoscrubber having acombined steering and drive system comprising two independentlycontrollable drive and steering torque mechanisms.

DESCRIPTION

Throughout the following description specific details are set forth inorder to provide a more thorough understanding to persons skilled in theart. However, well known elements may not have been shown or describedin detail to avoid unnecessarily obscuring the disclosure. Accordingly,the description and drawings are to be regarded in an illustrative,rather than a restrictive, sense.

Aspects of the invention provide autoscrubbers capable of being operatedin a manual (e.g. walk-behind) mode and an autonomous (operator free)mode, switching between such operational modes, methods for implementingsame and apparatus and methods for retrofitting existing walk-behindautoscrubbers to implement this functionality. In particular embodimentsand/or aspects of the invention, the autonomous control capability doesnot detract appreciably from an operator's ability to use theautoscrubber in a manual (walk-behind) mode.

Advantageously, some embodiments and/or aspects of the invention providea teach and repeat mode for autonomous control. Particular embodimentsand/or aspects of the invention comprise steering systems which use asingle positive torque mechanism to split positive driving torquebetween left and right drive wheels, while using individuallycontrollable steering torque mechanisms for each of the left and rightdrive wheels. In particular embodiments and/or aspects of the invention,the controllable steering torque mechanisms comprise negative torquemechanisms, each of which provides negative torque to (or impartsnegative torque on) its respective drive wheel and steers theautoscrubber through the application of negative torque differently tothe different drive wheels. In particular embodiments and/or aspects ofthe invention, the controllable steering torque mechanisms may provideboth positive and negative torque to their respective drive wheels. Insuch embodiments, steering may be implemented by application ofdifferent steering torque (positive and/or negative) to the differentdrive wheels. Particular embodiments and/or aspects of the inventionprovide a control mode which simulates a free-wheel effect. Inparticular embodiments and/or aspects of the invention, the steeringtorque mechanisms capture energy via regenerative braking when operatingin a negative toque mode.

FIG. 7 is a schematic illustration of an autoscrubber 101 according to aparticular embodiment. As explained in more detail below, autoscrubber101 may comprise a walk-behind autoscrubber retrofitted to provide botha manual (e.g. walk-behind) operational mode and an autonomous (operatorfree) operational mode. Additionally or alternatively, autoscrubber 101may comprise a new construction autoscrubber capable of operating inmanual (e.g. walk-behind) operational mode and autonomous (operatorfree) operational mode. Autoscrubber 101 comprises a chassis 700 whichsupports a cleaning system 701 used for cleaning floors and the like. Inthe particular case of the illustrated embodiment, cleaning system 701comprises a cleaning liquid dispensing tank 716, a cleaning liquiddispenser 704, a scrubbing head 702, a waste recovery system (typicallya squeegee and/or a vacuum) 710 and waste recovery tank 712. Inoperation (i.e. when cleaning), cleaning liquid dispensing tank 716feeds cleaning liquid (typically water mixed with cleaning solution(s))to scrubbing head 702 via cleaning liquid dispenser 704. Scrubbing head702 of the illustrated FIG. 7 embodiment comprises one or more(typically one or two) rotating or otherwise moveable brushes, which mayhave various shapes. The brush(es) of scrubbing head 702 may be moved byone or more suitable drive systems comprising suitable motors. In someembodiments, the brush(es) of the scrubbing head 702 are rotated (orotherwise moved) by an electric motor, either by direct coupling of themotor to the brush or with some form of speed reduction such as a gearbox, pulley system and/or the like. In some embodiments, the speed ofmovement of the brush(es) of scrubbing head 702 is adjustable. Themovement of the brush(es) of scrubbing head 702 together with thecleaning solution dispensed into scrubbing head 702 by cleaning liquiddispenser 704 cause the floors under autoscrubber 101 to be cleaned.Waste recovery system 710 (which in the illustrated FIG. 7 embodimentcomprises a squeegee and a vacuum) picks up the used cleaning liquid anddirt contained therein and stores same in waste recovery tank 712. Insome embodiments, the used cleaning liquid and dirt is passed through afilter and the filtered liquid is recycled back into the cleaning liquiddispensing tank 716.

Autoscrubber 101 of the illustrated FIG. 7 embodiment comprises a pairof drive wheels 102, 104 (only one of which is shown in FIG. 7) mountedto chassis 700. As explained in more detail below, the torque applied todrive wheels 102, 104 may be used to move autoscrubber 101 in bothmanual and autonomous operational modes and may be used to steerautoscrubber 101 in autonomous operational mode. Autoscrubber 101 of theillustrated FIG. 7 embodiment also comprises one or more castor wheels708 or other suitable form of idler (non-driven) wheels 708 mounted tochassis 700. Autoscrubber 101 of the illustrated FIG. 7 embodimentcomprises an operator interface 714, which in the illustrated embodimentcomprises a handle 714A and a control panel 714B. Handle 714A may begripped in the hand(s) of an operator for manual (e.g. walk-behind)operational mode. An operator may use handle 714A to steer autoscrubber101 when operating in manual mode. A control panel 714B may be used byan operator to adjust machine settings pertaining to cleaningfunctionality, such as but not limited to brush rotation speed, cleaningliquid dispensing rate and/or the like. As described in more detailbelow, control panel 714B may also be used to switch between autonomousand manual operating modes, initiate teach and/or repeat phases, saveand load path data, adjust operating speed, initiate and display systemdiagnostics, and configure and display various other machine settings.In some embodiments, control panel 714B is fixed onto autoscrubber 101.In some embodiments, control panel 714B is physically detached from theautoscrubber 101 and communicates with controller 116 of autoscrubber101 (e.g. through wired and/or wireless (e.g. Wi-Fi, Bluetooth, radiocommunications, and/or the like)). In some embodiments, control panel714B has a physical form factor. In some embodiments, control panel 714Bis a software application deployable onto conventional computers ormobile computing devices through the means of an app, program, webportal and/or the like. While being described as a panel for brevity,control panel 714B need not be implemented as a panel and may generallycomprise any user interface comprising machine input and/or machineoutput functionality and capable of operating in the manner describedherein.

Autoscrubber 101 shown in FIG. 7 and described above represents oneparticular type of autoscrubber which may be fabricated or retrofittedto incorporate various embodiments of the invention. Autoscrubbersincorporating various aspects of the invention need not comprise all orany of the specific features of the FIG. 7 autoscrubber 101. It will beappreciated from the description that follows that various embodimentsof the invention could be incorporated into a variety of differentautoscrubbers, some of which may be different in some respects thanautoscrubber 101 shown and described in FIG. 7. Example autoscrubbersmay include ride-on and chariot style autoscrubbers.

FIG. 1A depicts a schematic view of a steering system 100 for anautoscrubber 101 according to a particular embodiment. Autoscrubber 101and its steering system 100 are convertible between a manuallycontrolled operational mode and an autonomous operational mode. In someembodiments, steering system 100, which may be supported on the chassis700 of autoscrubber 101, may be retrofitted onto a conventionalwalk-behind autoscrubber to permit the walk-behind autoscrubber tooperate in a manually controlled operational mode and an autonomousoperational mode.

Steering system 100 of the FIG. 1 embodiment steers autoscrubber 101 byindependently controlling drive wheel speed for left drive wheel 102 andright drive wheel 104. It will be appreciated that, when drive wheels102, 104 rotate at different speeds, autoscrubber 101 will turn.Steering system 100 of the illustrated embodiment uses a single positivetorque mechanism 106 for providing positive torque to each of drivewheels 102, 104. This positive torque applied to drive wheels 102, 104propels autoscrubber 101 in a forward direction. Steering system 100 ofthe illustrated embodiment also comprises a pair of independentlycontrollable steering torque mechanisms 108, 109. Steering torquemechanisms 108, 109 are independently controllable to apply positivetorque (i.e. torque in a rotational direction consistent with the torqueapplied by positive torque mechanism 106) to their respective drivewheels 102, 104 and/or negative torque (i.e. braking, decelerationand/or some other torque in a rotational direction opposing thedirection of torque applied by positive torque mechanism 106 and, insome cases, in a rotational direction opposing any rotation of drivewheels 102, 104) to their respective drive wheels 102, 104. Steeringtorque mechanisms 108, 109 should be understood to include anyindependently controllable mechanisms for applying torque to drivewheels 102, 104, which may result in drive wheels 102 and 104 having twodifferent rotational velocities and/or cumulative output torque. Theindependently controllable nature of steering torque mechanisms 108, 109allows for independent control of rotational speeds and/or output torqueof drive wheels 102, 104. Steering of autoscrubber 101 may then beimplemented by causing drive wheels 102, 104 to rotate at differentspeeds.

FIG. 1B schematically illustrates an example steering system 100B whichrepresents a particular embodiment of the FIG. 1A steering system 100.In the FIG. 1B steering system 100B, steering torque mechanisms 108, 109are embodied by negative torque mechanisms 108′, 109′ which specificallyapply negative torque (e.g. braking or deceleration) to their respectivedrive wheels 102, 104 to achieve independent control of the rotationalspeeds and/or output torques of drive wheels 102, 104. FIG. 1Cschematically illustrates another example steering system 100C whichrepresents another particular embodiment of the FIG. 1A steering system100. The FIG. 1C steering system 100C differs from the FIG. 1B steeringsystem 100B in that, in the FIG. 1C steering system 100C, steeringtorque mechanisms 108, 109 are implemented by steering torque mechanisms108″, 109″ (described in more detail below) which are capable ofapplying negative torque and/or positive torque to their respectivedrive wheels 102, 104 to achieve independent control of the rotationalspeeds and/or output torques of drive wheels 102, 104. Positive torqueapplied to drive wheels 102, 104 by steering torque mechanisms 108″,109″ may be additional to the positive torque applied by positive torquemechanism 106.

During autonomous operational mode, torque mechanisms 106, 108, 109 arecontrolled by controller 116. Controller 116 is configured (e.g. usingsuitable hardware and/or software) to provide: suitable positive torquecontrol signals 211 to positive torque driver circuit 110 which in turnprovides suitable positive torque drive signals to positive torquemechanism 106; and suitable steering torque control signals 207, 209 tosteering torque driver circuits 112, 113 which in turn provide suitablesteering (e.g. positive steering or negative steering) torque drivesignals to steering torque mechanisms 108, 109. Controller 116 mayreceive input signals 214, 215 from rotation sensors 114, 115 (e.g.rotary encoders, tachometers or other suitable sensors) which mayrespectively measure or otherwise be indicative of rotationalcharacteristics of drive wheels 102, 104, from location and navigationsystem (LNS) 202, from user interface 714B and/or from other inputs (notshown). In some embodiments, LNS 202 may be implemented in whole or inpart by controller 116. As discussed in more detail below, controller116 may use these inputs to determine suitable positive torque controlsignals and steering control signals for controlling positive torquemechanism 106 and steering torque mechanisms 108, 109. Some embodimentsof steering torque mechanisms 108, 109 (e.g. where steering torquemechanisms 108, 109 comprise electric motors, as is the case in steeringsystem 100C of the FIG. 1C embodiment) may allow for recapture of energywhen torques applied by steering torque mechanisms 108, 109 are inopposition to the current velocity/momentum of autoscrubber 101. In thiscase, controller 116 may be connected to redistribute this power back toan energy storage device and/or power source (not shown), such as abattery, another type of charge storage device and/or the like.

Controller 116 may generally comprise any combination of hardware andsoftware capable of providing the functionality described herein. Forexample, controller 116 may be implemented in whole or in part on aprogrammed computer system comprising one or more processors, user inputapparatus, displays and/or the like. Controller 116 may be implementedin whole or in part as an embedded system comprising one or moreprocessors, user input apparatus, displays and/or the like. Processorsmay comprise microprocessors, digital signal processors, graphicsprocessors, field programmable gate arrays, and/or the like. Componentsof controller 116 may be combined or subdivided, and components ofcontroller 116 may comprise sub-components shared with other componentsof controller 116. Components of controller 116, may be physicallyremote from one another. Controller 116 may be connected (e.g. withsuitable electrical connections (not expressly shown in FIG. 1)) todeliver control signals 211, 207, 209 to drive circuits 110, 112, 113.Controller 116 may be configured (e.g. using suitable software, logicconfiguration and/or the like) to use those control signals 211, 207,209 to control the drive currents driven by drive circuits 110, 112, 113into positive torque mechanism 106 and steering torque mechanisms 108,109 to thereby control the torque applied to wheels 102, 104.

In the particular case of the illustrated embodiment of FIG. 1, positivetorque mechanism 106 may comprise a transaxle 106A which is mechanicallyconnected between drive motor 106B and wheels 102, 104 to split positivetorque from motor 106B to drive wheels 102, 104. Transaxle 106Aadvantageously permits drive wheels 102, 104 to rotate at differentspeeds while still splitting torque from drive motor 106B (e.g. equallyor at least approximately equally) between wheels 102, 104. In someembodiments, however, positive torque mechanism 106 may comprise othersuitable mechanisms for mechanically connecting one or more drive motorsto drive wheels 102, 104. By way of non-limiting example, some positivetorque mechanisms 106 may comprise rotary electric motors (such as DCbrushed motors, DC brushless motors, AC inductor motors, AC synchronousmotors, electric linear induction motors and/or the like); heat engines(such as two-stroke combustion engines, four-stroke combustion engines,rotary engines and/or the like); compressed gas or pneumatic poweredsystems; spring wound systems and/or the like.

In the particular case of steering system 100B in the illustratedembodiment of FIG. 1B, steering torque mechanism 108 may comprise abrake mechanism 108A which may apply force to drive wheel 102 in amanner which generates torque in direction opposed to the torque appliedby positive torque mechanism 106 or reduces the net torque applied todrive wheel 102 in the direction applied by positive torque mechanism106. In the illustrated embodiments, brake mechanism 108A comprises aV-brake mechanism 108A or similar caliper mechanism which applies asqueezing force to drive wheel 102 at a particular radius. Thissqueezing force acts in a direction that is approximately parallel tothe axis about which drive wheel 102 rotates. A friction force that ispositively correlated with the squeezing force, generated by contact ofthe brake mechanism 108A onto drive wheel 102, generates a negativetorque on the drive wheel 102 (in this case, a torque that opposes anydirection of angular movement of drive wheel 102 about its axis). Insome embodiments, rather than applying a squeezing force in a directionthat is approximately parallel to the axis of rotation of drive wheel102, other forces may be applied to drive wheel 102 to create negativetorque. For example, a force may be applied in a direction normal (orapproximately normal) to the surface of drive wheel 102. As anotherexample, in some embodiments, a force may be applied in a direction thatis a combination of parallel to the axis of rotation and normal to thesurface of the wheel. In some embodiments, rather than applying forcedirectly to drive wheel 102 itself, brake mechanism 108A may beconfigured apply force to a disc (not shown), or to some otherintermediate member, which is rigidly or otherwise connected to rotatewith, or otherwise move with the rotation of, drive wheel 102.

In the particular case of steering system 100B in the illustratedembodiment of FIG. 1B, brake 108A of steering torque mechanism 108comprises an actuation mechanism which may comprise a motor (e.g. astepper motor) 108D operatively connected to a winch take-up 108C whichreels cable 108B connected to brake 108A. Rotation of motor 108D in afirst angular direction causes cable 108B to be wound onto winch take-up108C, thereby increasing the negative (braking) torque applied bysteering torque mechanism 108 to drive wheel 102; and rotation of motor108D in a second (opposite) angular direction causes cable 108B to bereleased from winch take-up 108C, thereby decreasing the negative(braking) torque applied by steering torque mechanism 108 to drive wheel102. Advantageously, stepper motor 108D may provide a high resolution tothe negative (braking) torque applied by steering torque mechanism 108to drive wheel 102.

In some embodiments, negative torque mechanism 108 may comprise othersuitable mechanisms for mechanically applying negative (braking) torqueto drive wheel 102 (or to some suitable intermediate member). By way ofnon-limiting example, such steering torque mechanisms 108 may comprise:different forms of brake mechanisms (e.g. disc brakes in the place ofV-brakes 108A); different forms of actuator (e.g. hydraulic actuation inthe place of cables 108B and winch 108C; linear actuators in the placeof stepper motor 108D; or the like); electric eddy current brakes;electric regenerative brakes; mechanical regenerative brakes (e.g.comprising flywheels, springs, gravity masses or the like); viscousdampers (e.g. fans, linear dampers or the like); and/or the like.

Steering torque mechanism 109 may comprise components similar to thoseof steering torque mechanism 108 which may be suitably modified forapplication of positive or negative torque to drive wheel 104 or to adisc (not shown), or to some other intermediate member, which is rigidlyor otherwise connected to rotate with, or otherwise move with therotation of, drive wheel 104.

FIG. 1C depicts a steering system 100C according to another exampleembodiment. In the particular case of steering system 100C depicted inthe illustrated embodiment of FIG. 1C, steering torque mechanisms 108,109 each comprise a DC steering motor 108E, 109E outfitted with a runnerwheel 108G, 109G and a suitable speed-adjusting transmission or gearbox108F, 109F. Runner wheels 108G, 109G turn in unison with (or at leastwith minimal slippage relative to) drive wheels 102, 104 of autoscrubber101. The two sets of wheels (runner wheels 108G, 109G and drive wheels102, 104) may be mechanically linked (runner wheel 108G to drive wheel102 and runner wheel 109G to drive wheel 104) via friction between thewheel surfaces and suitably located and/or shaped mounts (e.g. tochassis 700). This connection between runner wheels 108G, 109G and drivewheels 102, 104 could additionally or alternatively be accomplished bymeans of gears, chains, belts, shaft coupling, or any other suitablemechanical linkage, which may or may not change the relative rotationalspeeds of runner wheels 108G, 109G and drive wheels 102, 104. Torque canbe transferred in either direction (i.e. from drive wheels 102, 104through runner wheels 108G, 109G and transmissions 108F, 109F tosteering motors 108E, 109E, and/or from steering motors 108E, 109E viatransmissions 108F, 109F and runner wheels 108G, 109G to drive wheels102, 104).

In steering system 100C of the illustrated FIG. 1C embodiment, rotationsensors 114, 115 respectively provide sensor signals 214, 215 whichcomprise measurements or are otherwise indicative of the rotationalcharacteristics (e.g. relative angular position, angular velocity and/orthe like) of runner wheels 108G, 109G, and send this information tocontroller 116. It will be appreciated that where there is no slippage(or limited slippage) between runner wheels 108G, 109G and theirrespective drive wheels 102, 104, the rotational characteristics ofrunner wheels 108G, 109G may be converted by system controller 116 intorotational characteristics of drive wheels 102, 104. Accordingly,rotation sensors 114, 115 may be considered to provide feedback signals214, 215 indicative of the rotational characteristics of both runnerwheels 108G, 109G and drive wheels 102, 104. Such rotationalcharacteristics of runner wheels 108G, 109G and/or drive wheels 102, 104could also be gathered at the steering motors 108E, 109E, or drivewheels 102, 104.

In the illustrated embodiment, controller 116 receives (as inputs)feedback signals 214, 215 from rotation sensors 114, 115 which aremeasurements or otherwise indicative of the rotational characteristics(e.g. relative angular position, angular velocity and/or the like) ofwheels 102, 104 (and/or, in some embodiments, runner wheels 108G, 109G).As will be appreciated by those skilled in the art, suitable signalconditioning circuitry (e.g. amplifiers, buffers, filters, analog todigital converters and/or the like—not expressly shown) may be providedbetween rotation sensors 114, 115 and controller 116. In the illustratedembodiment, controller 116 also receives (as inputs) left wheel andright wheel velocity reference signals 203, 205 from LNS 202 (see FIG.1A) and/or from user interface 714B (FIG. 7). As discussed above, insome embodiments, LNS 202 may be implemented in whole or in part bycontroller 116, in which case controller 116 may not receive left wheeland right wheel velocity reference signals 203, 205 as inputs, but mayinstead generate left wheel and right wheel velocity reference signals203, 205 as internal variables or signals. A control objective ofcontroller 116 may be to cause drive wheels 102, 104 to track velocityreference signals 203, 205.

In the illustrated embodiment, as discussed above, controller 116generates, as output signals: a positive torque control signal 211 whichis provided to positive torque driver circuit 110; a left wheel steeringtorque control signal 207 which is provided to left wheel steeringtorque driver circuit 112; and a right wheel steering torque controlsignal 209 which is provided to right wheel steering torque drivercircuit 113. Controller 116 may use its inputs (e.g. the feedbacksignals 214, 215 from rotation sensors 114, 115 and left wheel and rightwheel velocity reference signals 203, 205) as a basis for determiningits outputs (e.g. the positive torque control signal 211 and the leftand right wheel steering torque control signals 207, 209) and maythereby execute desired behaviors. In particular, controller 116 mayimplement suitable feedback-based (closed loop) control technique or acombination of closed loop and open loop control techniques to cause thevelocities of left and right wheels 102, 104 to track left wheel andright wheel velocity reference signals 203, 205. It will be appreciatedthat causing left and right wheels 102, 104 to rotate with differentvelocities will cause autoscrubber 101 to change its orientation (e.g.to steer). The specific nature of the behaviors implemented bycontroller 116 may depend on whether autoscrubber 101 is operating inautonomous operation mode or manual operational mode, as explained inmore detail below.

In the illustrated embodiment, steering torque driver circuits 112, 113and positive torque driver circuit 110 may comprise suitable electronicdrive components for supplying suitable torque drive signals to steeringtorque mechanisms 108, 109 and positive torque mechanism 106 based onthe corresponding torque control signals 211, 207, 209 received fromcontroller 116. Such torque drive signals 211, 207, 209 may compriseelectronic signals with suitable voltages, currents, duty cycles, powerand/or other electronic characteristics suitable for controlling theirrespective steering torque mechanisms 108, 109 and positive torquemechanism 106. Such electronic driver circuits 110, 112, 113 maycomprise pulse-width modulation (PWM) based driver circuits or any of awide variety of other types of driver circuits which are well known inthe art and are not described further herein.

Autoscrubber 101 may have two operational modes: autonomous operationalmode and manual (walk-behind) operational mode. In some embodiments,steering system 100 of autoscrubber 101 is retrofitted onto an existingwalk-behind manual controlled autoscrubber to provide dual modeautoscrubber 101. An operator can switch autoscrubber 101 from manualoperational mode to autonomous operational mode (and vice versa) usingsome suitable switch, button, slider and/or the like (e.g. at userinterface 714B).

FIG. 2A is a schematic depiction of a number of components ofautoscrubber 101 implementing steering system 100B (FIG. 1B) inautonomous operational mode as described above. It can be seen from FIG.2A, that when operating in autonomous operational mode, LNS 202 isactive and steering system 100B controls negative torque mechanisms108′, 109′ and positive torque mechanism 106. FIG. 2B is a schematicdepiction of a number of components of autoscrubber 101 implementingsteering system 100B (FIG. 1B) in a manual operational mode. It can beseen, from FIG. 2B and from contrasting FIG. 2B with FIG. 2A, that inmanual (walk-behind) operational mode, LNS 202 is de-activated, there isno control of negative torque mechanisms 108′, 109′ and a user interface(e.g. control panel 714B of operator interface 714) and associatedcircuits 206 may be used to control positive torque mechanism 106. Insome embodiments, negative torque mechanisms 108′, 109′ may bephysically decoupled from wheels 102, 104 in manual operational mode.For example, in the case of steering system 100B of the illustratedembodiment of FIG. 1B, brake mechanism 108A can be physically decoupledfrom drive wheel 102 (and negative torque mechanism 109′ can besimilarly physically decoupled from drive wheel 104) to permit drivewheels 102, 104 to rotate without the influence of negative torquemechanisms 108′, 109′. In some embodiments, autoscrubber 101 can beconfigured such that, in manual operational mode, a user may be able tocontrol negative torque mechanisms 108′, 109′ using user control panel714B and associated circuits 206.

FIG. 2C is a schematic depiction of a number of components ofautoscrubber 101 implementing steering system 100C (FIG. 1C) inautonomous operational mode as described above. It can be seen from FIG.2C, that when operating in autonomous operational mode, LNS 202 isactive and controller 116 controls steering torque mechanisms 108″, 109″and positive torque mechanism 106. More specifically, in the particularcase of the illustrated FIG. 2C embodiment, controller 116 is shownimplementing closed loop speed control for steering torque mechanisms108″, 109″ and controller 116 is shown implementing open loop speedcontrol for positive torque mechanism 106. This is not necessary. Insome embodiments, closed loop control can also be implemented forpositive torque mechanism 106. Further control techniques are describedin more detail below.

FIG. 2D is a schematic depiction of a number of components ofautoscrubber 101 implementing steering system 100C (FIG. 1C) in manualoperational mode as described above. As is the case with FIG. 2Bdescribed above, LNS 202 is de-activated and a user interface (e.g.control panel 714B of operator interface 714) and associated circuits206 may be used to control positive torque mechanism 106. However,unlike the case of FIG. 2B described above, in the particular case ofsteering system 100C of the FIG. 1C embodiment, runner wheels 108G. 109Gare held in continuous contact with drive wheels 102, 104 and steeringtorque mechanisms 108″, 109″ are not physically decouplable from drivewheels 102, 104 in autonomous mode. Consequently, controller 116 mayimplement feedforward based “freewheeling” control.

An objective of freewheeling control is to supply suitable controlsignals 207, 209 to steering torque drive circuits 112, 113 such thatdrive circuits drive steering torque motors 108E, 109E in such a mannerthat a user autonomously operating autoscrubber 101 is not aware of ordoes not feel the resistance that might otherwise be applied to rotationof drive wheels by steering torque mechanisms 108″, 109″—i.e. such thatrunner wheels 108G, 109G rotate as though they are “freewheeling”without corresponding mechanical linkages to steering torque motors108E, 109E.

A schematic flow chart showing a method 220 for implementing feedforwardfreewheeling control is shown in FIG. 2E. The objective of the FIG. 2Emethod 220 is to establish zero (or acceptably close to zero) current insteering motors 108E, 109E. Method 220 starts in block 222 whichinvolves an inquiry into whether autoscrubber 101 is in manual mode. Ifthe block 222 inquiry is negative, then method 220 proceeds to block 224which involves implementing autonomous operational mode or an idle mode,while waiting for manual mode to occur again If the block 222 inquiry ispositive, then method 226 proceeds to block 226. Block 226 involvesacquiring sensor data. In the particular case of the illustrated (FIG.1C) embodiment, the sensor data acquired in block 226 may compriserotational data indicative of the rotational characteristics of runnerwheels 108G, 109G and similarly indicative of rotational characteristicsof steering motors 108E, 109E. In other embodiments, additional oralternative sensors can be used in block 226 to measure or obtain othermeasurements indicative of the operational characteristics of steeringmotors 108E, 109E. By way of non-limiting example, such sensors couldcomprise current sensors connected to measure the current throughsteering motors 108E, 109E. Method 220 then proceeds to block 228 whichinvolves using a model of steering motors 108E, 109E or empiricallydetermined characteristics of steering motors 108E, 109E to predict aback EMF. It will be appreciated by those skilled in the art that whensteering motors 108E, 109E rotate (because of runner wheels 108G, 109Gattached to drive wheels 102, 104), steering motors 108E, 109E willgenerate a back EMF. With a suitable model (e.g. a no-load model) ofsteering motors 108E, 109E and/or with empirically determinedoperational characteristics (e.g. no load operational characteristics)associated steering motors 108E, 109E, controller 116 can use the block226 sensor data to predict a corresponding back EMF. A mapping betweenthe block 226 sensor data and the predicted back EMF may be maintainedin a suitable look up table or the like which may be accessible tocontroller 116.

In one particular embodiments, the block 226 model can be obtainedempirically by using PWM duty cycles with a range from 0%-100% and thenrecording the corresponding rotational speed of the motor under no loadconditions. The model can be obtained for both positive and negativerotational directions. In some embodiments, these empirically determineddata points can be maintained in a look up table accessible tocontroller 116. In some embodiments, these empirically determined datapoints can be fit to a suitable curve (e.g. a;linear curve) and then thecurve's parameters can be used by controller 116 to make the block 228predictions.

Once the back EMF is predicted in block 228, method 220 proceeds toblock 230, which involves determining suitable steering control signals207, 209 which will cause the desired back EMF (or an equivalenteffective PWM signal) to be applied to steering motors 108E, 109E.Controller 116 may output these signals as control signals 207, 209 tosteering torque drivers 112, 113. With these signals, steering torquedrivers 112, 113, drive suitable drive signals to steering motors 108E,109E which effectively cause the current in steering motors 108E, 109Eto be zero or near zero. Accordingly, when a user operates autoscrubber101 in manual mode, the user obtains the sensation that autoscrubber isoperating like a conventional walk-behind autoscrubber because theautoscrubber is “freewheeling” independent of the resistance that wouldotherwise be caused by steering torque mechanisms 108″, 109″. Asdiscussed above in connection with FIG. 2D, forward velocity/power maybe requested by the user at user interface 714B and may be implementedin an open loop manner, and steering is provided by the user who applieslateral forces at handle(s) 714A. Application of lateral forces allowsthe user to easily steer autoscrubber 101 by increasing the velocity ofone wheel 102, 104 and/or decreasing the velocity of the other wheel104, 102. At the conclusion of block 230, method 220 loops back to block222 for another iteration.

In other embodiments, steering torque mechanisms 108″, 109″ of the FIG.1C steering system 100C could be made to be physically decouplable fromdrive wheels, so that freewheeling control is not required.

FIG. 10 is block diagram representation of a feedback controlsystem/algorithm 280 suitable for controlling the FIG. 1C steeringsystem 100C of the FIG. 1 autoscrubber 101 in autonomous mode accordingto a particular embodiment. The FIG. 10 control algorithm may beimplemented by controller 116. Controller 116 uses velocity feedbacksignals 214, 215 from rotation sensors 114, 115 to implement PIDvelocity control loops for each of steering torque mechanisms 108, 109(represented in FIG. 10 by their corresponding steering motors 108E,109E and runner wheels 108G, 109G). As discussed above, rotation sensors114, 115 may be operatively connected to left and right drive wheels102, 104 and/or to left and right runner wheels 108G, 109G. In the FIG.10 embodiments, the PID loops for the left and right runner wheels 108G,109G (and/or the left and right drive wheels 102, 104) are independentand informationally isolated from one another, and executed via controlsignals 207, 209 sent to steering torque mechanisms 108, 109 (and moreparticularly to their driver circuits 112, 113—not shown in FIG. 10, butsee FIG. 1C and discussion above). In the illustrated FIG. 10embodiment, control signals 207, 209 are determined by PID blocks 282,284 of controller 116. In the illustrated embodiment of FIG. 10,positive torque mechanism 106 is controlled in an open-loop manner,based on known motor performance characteristics (which may be stored inlook up table 285) and velocity reference commands/signals 203, 205issued by LNS 202. Velocity reference commands 203, 205 are issued fromLNS 202 in the form of desired right and left wheel 102, 104 velocitysetpoints, which controller 116 uses as input for each of the threecontrol loops.

The type of dual isolated PID and single open-loop control scheme shownin FIG. 10 could also be implemented with different feedbackinformation. Other implementations could be torque-based, relying onfeedback information from current sensors in lieu of or in addition torotation sensors 114, 115. A modified implementation of this controlscheme is modified to use velocity feedback information 214, 215 fromboth drive wheels 102, 104 (or roller wheels 108G, 109G) to controlpositive drive torque mechanism 106 in a closed-loop manner based onsuch feedback, rather than in an open-loop manner. It will beappreciated that the FIG. 10 control system 280 could be used with theFIG. 1B steering system 100B by substituting negative torque mechanisms108′, 109′ for steering motors 108E, 109E.

An additional or alternative control technique utilizes a MIMO (MultiInput Multi Output) control system/algorithm to control left and rightwheel velocities (e.g. for drive wheels 102, 104 or roller wheels 108G,109G). FIG. 11 is block diagram representation of a feedback controlsystem/algorithm 380 suitable for controlling the FIG. 1C steeringsystem 100C of the FIG. 1 autoscrubber 101 in autonomous mode using aMIMO approach according to a particular embodiment. The FIG. 11 controlsystem/algorithm 380 may be implemented by controller 116. Controller116 receives (as inputs) left and right wheel velocities, in the form offeedback signals 214, 215 provided by suitable rotational sensors 114,115 (not expressly shown in FIG. 11, but see FIG. 1C) and also the leftand right wheel velocity reference signals 203, 205 coming from LNS 202.Controller 116 outputs torque control signals 207, 209 for steeringtorque mechanisms 108,109 (see FIG. 1) and torque control signal 211 forpositive torque mechanism 106. The FIG. 11 illustration also omitsdriver circuits 110, 112, 113 (shown in FIGS. 1B and 1C) to avoidobfuscating the control features.

Control system/algorithm 380 comprises two feedback loops—one for eachof steering torque mechanisms 108, 109 and corresponding wheels 102,104. First summing junctions 406A, 406B determine errors between thedesired (reference) wheel velocities 203, 205 and the feedbackvelocities 214, 215. These errors are integrated by integrators 408A,408B and the integrated results are scaled by integral gains. Controlsystem/algorithm 380 comprises six integral gains (three gains for eachsteering torque mechanism 108, 109 and corresponding wheel 102, 104) asfollows:

-   -   KiRR: Right steering mechanism torque based on right wheel speed        error;    -   KiMR: Transaxle (Positive Torque Mechanism) based on right wheel        speed error;    -   KiLR: Left steering mechanism torque based on right wheel speed        error;    -   KiRL: Right steering mechanism torque based on left wheel speed        error;    -   KiML: Transaxle (Positive Torque Mechanism) based on left wheel        speed error; and    -   KiLL: Left steering mechanism torque based on left wheel speed        error.

Control system/algorithm 380 also comprises six gains (referred to asproportional gains) which are applied directly to the feedback signals214, 215 from rotational sensors 114, 115. The six proportional gains(three gains for each steering torque mechanism 108, 109 andcorresponding wheel 102, 104) include:

-   -   KRR: Right steering mechanism torque based on right wheel speed        (not speed error);    -   KMR: Transaxle torque based on right wheel speed;    -   KLR: Left steering mechanism torque based on right wheel speed;    -   KRL: Right steering mechanism torque based on left wheel speed;    -   KML: Transaxle torque based on left wheel speed; and    -   KLL: Left steering mechanism torque based on left wheel speed.

A purpose of the various gains is to determine how much torque is neededto achieve desired wheel speeds. In the FIG. 11 control system/algorithm380, the outputs from the corresponding integral gains and thecorresponding proportional gains are added to one another at summingjunctions 382, 384, 386 (for the right wheel feedback 215) and atsumming junctions 388, 390, 392 (for the left wheel feedback 214). Forexample, the output of integral gain KiRR is added to proportional gainKRR at summing junction 382, the output of integral gain KiRL is addedto proportional gain KRL at summing junction 388 and so on. Then, theoutputs from summing junctions 382 and 392 are summed together atsumming junction 394 (for right steering torque mechanism 109), theoutputs from summing junctions 384 and 390 are summed together atsumming junction 396 (for the positive torque mechanism 106) and theoutputs from summing junctions 386, 388 are summed together at summingjunction 398 (for left steering torque mechanism 108) to result incorresponding control signals 209 (for right steering torque mechanism109), control signal 211 (for positive torque mechanism 106) and 207(for left steering torque mechanism 108).

The following mathematics illustrates the principles of the FIG. 11control system/algorithm 380. The left and right wheels 102, 104 of thetransaxle may be modelled using the following differential equations:

$\begin{matrix}{{{J_{L}{\overset{¨}{\theta}}_{L}} + {B_{L}{\overset{.}{\theta}}_{L}}} = {\frac{T_{M}}{2} - T_{L} + T_{R}}} & \left( {1a} \right) \\{{{J_{R}{\overset{¨}{\theta}}_{R}} + {B_{R}{\overset{.}{\theta}}_{R}}} = {\frac{T_{M}}{2} - T_{R} + T_{L}}} & \left( {1b} \right)\end{matrix}$Where J_(L) and J_(R) are the rotational inertia of the left and rightwheels and B_(L) and B_(R) are the viscous frictions of the left andright wheels. T_(M), T_(L), and T_(R) are the transaxle (positive)torque, left steering torque, and right steering torque respectively.The system of equations (1a) and (1b) can be rearranged to have thefollowing state space equation:

$\begin{matrix}{\begin{bmatrix}{\overset{¨}{\theta}}_{L} \\{\overset{¨}{\theta}}_{R}\end{bmatrix} = {{\begin{bmatrix}{- \frac{B_{L}}{J_{L}}} & 0 \\0 & {- \frac{B_{R}}{J_{R}}}\end{bmatrix}\begin{bmatrix}{\overset{.}{\theta}}_{L} \\{\overset{.}{\theta}}_{R}\end{bmatrix}} + {\begin{bmatrix}\frac{1}{J_{L}} & \frac{1}{J_{L}2} & {- \frac{1}{J_{L}}} \\{- \frac{1}{J_{R}}} & \frac{1}{J_{R}2} & \frac{1}{J_{R}}\end{bmatrix}\begin{bmatrix}T_{R} \\T_{M} \\T_{L}\end{bmatrix}}}} & (2)\end{matrix}$To control the equation (2) state space system control system/algorithm380 may use a state space pole placement controller with integrator. Thecommand torques T_(M), T_(L), and T_(R) may be provided as follows:

$\begin{matrix}{\begin{bmatrix}{\overset{¨}{\theta}}_{L} \\{\overset{¨}{\theta}}_{R} \\e_{L} \\e_{R}\end{bmatrix} = {\quad{\begin{bmatrix}{{- \frac{B_{L}}{J_{L}}} + \frac{K_{RL} + \frac{K_{ML}}{2} - K_{LL}}{J_{L}}} & \frac{K_{RR} + \frac{K_{MR}}{2} - K_{RL}}{J_{L}} & \frac{K_{iRL} + \frac{K_{iML}}{2} - K_{iLL}}{J_{L}} & \frac{K_{iRR} + \frac{K_{iMR}}{2} - K_{iLR}}{J_{L}} \\\frac{{- K_{RL}} + {K_{ML}/2} + K_{LL}}{J_{R}} & {{- \frac{B_{R}}{J_{R}}} + \frac{{- K_{RR}} + {K_{MR}/2} + K_{RL}}{J_{R}}} & \frac{{- K_{iRL}} + {K_{iML}/2} + K_{iLL}}{J_{R}} & \frac{{- K_{iRR}} + {K_{iMR}/2} + K_{iLR}}{J_{R}} \\{- 1} & 0 & 0 & 0 \\0 & {- 1} & 0 & 0\end{bmatrix}{\quad{\left\lbrack \begin{matrix}{\overset{.}{\theta}}_{L} \\{\overset{.}{\theta}}_{R} \\{\int{e_{L}{dt}}} \\{\int{e_{R}{dt}}}\end{matrix} \right\rbrack + {\begin{bmatrix}0 & 0 \\0 & 0 \\1 & 0 \\0 & 1\end{bmatrix}\begin{bmatrix}\omega_{L} \\\omega_{R}\end{bmatrix}}}}}}} & (3)\end{matrix}$where ω_(L) and ω_(R) are the commanded wheel velocities 203, 205.

It will be appreciated that the continuous time equations (1a), (1b),(2) and (3) may be discretized for the purposes of digitalimplementation by controller 116. It will be further appreciated thatthe FIG. 11 control system 380 could be used with the FIG. 1B steeringsystem 100B by substituting negative torque mechanisms 108′, 109′ forsteering torque mechanisms 108″, 109″ shown in FIG. 11.

The switching of the various systems between manual and autonomousoperational modes may be effected by conventional switches, relays,software switches and/or the like. When LNS 202 is in passive mode (i.e.autoscrubber is in manual operational mode), LNS 202 does not provideleft and right wheel velocity reference signals 203, 205 to controller116. However, LNS system 202 may still be operational and may collectsensor data (as described in more detail below). When LNS 202 is inactive mode, LNS 202 may provide left and right wheel velocity referencesignals 203, 205 to controller 116, as described above. In manualoperational mode, autoscrubber 101 may be operated in the same manner asconventional walk-behind autoscrubbing machines, where the user selectsthe forward speed with a knob, slider or other user input on userinterface 714B and steers autoscrubber 101 by physically turning themachine.

In addition to manually operating autoscrubber 101 in the mannerdiscussed above, some embodiments may provide the ability for remoteoperation and monitoring of autoscrubber 101. Remote operation andmonitoring of autoscrubber 101 may be used to connect to autoscrubber101 from a remote location for diagnostics, operation and/or the like.FIG. 8 shows a schematic representation of a remote monitoring system250 which may be used to connect to autoscrubber 101 for diagnostics,operation and/or the like. A remotely located user may control variousaspects of autoscrubber 101 using a PC user interface 252 or mobile userinterface 254 which may be located remotely from autoscrubber 101. PCuser interface 252 and/or mobile user interface 254 may connect toautoscrubber 101 via a cloud server 258 to which autoscrubber 101 may bewirelessly connected. The connection of PC user interface 252 and/ormobile user interface 254 to cloud server 258 may be via wireless accesspoint 256 or may be wireless. User interfaces 252, 254 may permit theuser to control different aspects of autoscrubber 101, such as, by wayof non-limiting example, running pre-defined test procedures; runningcommands to access system logs and diagnostics features; movingautoscrubber 101 around while collecting sensor data to assess theenvironment; and/or the like. User interfaces 252, 254 may be used tovisualize messages being passed in the network such as readings fromvision sensor, navigation sensor, attitude sensor, odometry, proximitysensors, robot diagnostics, command signals to actuators and/or thelike. Cloud server 258 may manage traffic between autoscrubber and userinterfaces 252, 254 and may be additionally or alternatively be used asintermediate processing node to minimize excessive network traffic usingintelligent algorithms, such as data compression algorithms, environmentsimulation for training and collaborative control. Remote monitoringsystem 250 may optionally comprise a user-input device 260, such as ajoystick or the like which may be useful when remotely operatingautoscrubber 101.

The following represents an example use case for remote monitoringsystem 250 of FIG. 8. A remote operator may receive a feed from a visionsensor on PC user interface 252 (e.g. on a display device attached to aremote PC running suitable user interface software for interacting withautoscrubber 101). The vision sensor may be mounted on a pan-tilt gimbalon autoscrubber 101. The pan-tilt gimbal may connect to controller 116of autoscrubber 101 via a microcomputer based serial interface. The usermay then use user interface 252 to send suitable commands toautoscrubber 101 to operate the gimbal via a virtual private networkhosted on cloud server 258. Additionally, the remote user may receive afeed from a vision sensor on autoscrubber 101 via a mobile applicationwhich implements mobile user interface 254 on a corresponding mobilecomputing device. The user may then communicate with autoscrubber 101 toprovide suitable commands to operate the gimbal. The controls to operatethe gimbal may be captured, for example, by sensing head movementcaptured using a suite of motion sensors in mobile user interface 254 orby suitable image interpretation software.

In some embodiments, other functions (such as, by way of non-limitingexample, control of cleaning motors, vacuums, scrubber deployment,squeegee deployment, and liquid dispensers and/or the like) may also beaccomplished via user interface 714B. The details of the control of suchfunctionalities may be substantially similar to that of conventionalwalk-behind autoscrubbers and is not described in further detail here.In some embodiments, however, one or more of these functionalities maybe controlled by controller 116 during autonomous and/or manualoperational modes.

LNS 202 is a localization and navigation system 202 which, as its nameimplies, may locate autoscrubber 101 in an environment and may controlthe movement of (i.e. navigate) autoscrubber 101 when autoscrubber 101is in an autonomous operational mode. LNS 202 may control the movementof autoscrubber 101 by providing suitable left and right wheel velocitysignals 203, 205 which may be controllably tracked by steering system100 and which may cause autoscrubber 101 to move and steer, as describedabove. In some embodiments, LNS 202 uses a “teach and repeat” approachwhereby an operator “teaches” a path for autoscrubber 101 to follow (inmanual operational mode) by manually guiding autoscrubber 101 along thedesired path while indicating start and end locations and LNS 202 causesautoscrubber 101 to repeat the path (in autonomous operational mode)when the operator positions autoscrubber anywhere on (or near) the pathand initiates the repeat program.

FIG. 3 is a state machine representation of LNS 202 according to aparticular embodiment. In the illustrated embodiment, the states of LNS202 are divided into teach mode (comprising states A, B and C) andrepeat mode (comprising states D, E, F, G, H, and I). Generallyspeaking, in teach mode, an operator demonstrates a path forautoscrubber 101 to follow (in manual operational mode) by manuallyguiding autoscrubber 101 along the desired path while indicating startand end locations; and, in repeat mode, LNS 202 causes autoscrubber 101to repeat the path (in autonomous operational mode) when the operatorpositions autoscrubber anywhere on (or near) the path and initiates therepeat program.

In state A, an operator positions autoscrubber 101 to a start of a pathand engages teach mode. LNS then proceeds to state B, where the operatormanually guides autoscrubber through a desired path using conventionalmanual walk-behind operation, as discussed above. During the movement ofautoscrubber 101 along the desired path in state B, autoscrubber 101records data from various sensors with the purpose of recording theparticulars of the desired path in a manner that will facilitateautoscrubber 101 subsequently traversing the desired path autonomouslyin repeat mode.

FIG. 5 shows an example path 300 along which an operator may guideautoscrubber 101 in state B. In the example path 300 of FIG. 5, anoperator guides autoscrubber 101 along the path 300 from start 309 toend 311. Data from the various sensors are recorded. In someembodiments, the various sensors include odometry sensors 114, 115 (e.g.encoders relating to the rotational characteristics of wheels 102, 104),forward and upward facing camera(s) 119 (see FIGS. 1A, 1B, 1C) forrecording visual features or cues from the ceiling, walls, and objectsin the environment, inertial measurement units, range sensors 121 (e.g.laser scanners, depth sensors (e.g. infrared projection cameras),sonars, infrared range finders and/or the like) and/or the like. FIG. 5also depicts visual cues 314 in the environment (represented as stars inFIG. 5) and structures 316 in the environment (represented as trianglesin FIG. 5). It will be appreciated that structures 316 in theenvironment provide feedback for range sensors 121 and may also providevisual cues for cameras 119. In terms of processing or otherwise dealingwith the data received from the various sensors, LNS 202 may parse thisdata into a series of discrete nodes 302 along path 300. Path 300 may bebroken down in terms of segments 304 between nodes 302. Each segment 304has a start node 302 and end node 302, with the end node 302 of onesegment 304 being the start node 302 of the next segment 304. In theexemplary path 300 shown in FIG. 5, nodes 302 are numbered N₁, N₂, N₃ .. . N_(i−1), N_(i).

For each node 302, LNS 202 records sensor data which may include,without limitation: odometry values, accelerometer data, laser scans,point clouds, depth information, range data relating to structures 316detected by range sensors 121, the identity of visual features 314observed by camera(s) 119, where the visual features 314 are located inthe field of view of camera(s) 119 and/or relative to the autoscrubber101, the orientation of the visual features 314 relative to theorientation of autoscrubber 101, and/or the like. In some embodiments,the various characteristics of visual features 314 may be identified orotherwise determined using suitable image processing tools, such as, byway of non-limiting example, OpenCV and/or the like. OpenCV is an opensource computer vision and machine learning software library. Features314 that are typically detected using OpenCV include those with highimage contrast, such as corners and/or the like. Techniques for usingOpenCV and the detection of visual features 314 using OpenCV and/orother computer vision techniques are well known by those skilled in theart. In some embodiments, consecutive laser scans (or other rangesensors) 121 captured in a plane can be processed to create one or moretwo-dimensional grid maps. A laser scan is a set of range measurementsthat originate from the same point and can be acquired via a LIDAR(Light, Imaging, Detection And Ranging) sensor. Many existing techniquesfor generating two-dimensional grid maps (such as iterative closestpoint, pose graph SLAM (Simultaneous Localization And Mapping) and/orthe like) using information from laser scans (or other range sensors)121 are well known by those skilled in the art. As explained in moredetail below, the data recorded at each node 302 may be used in therepeat mode. Processing of sensor data into nodes 302 along path 300 cantake place in real time (e.g. while the operator is manually controllingautoscrubber 101 in manual operational mode) and/or at the conclusion ofthe teach phase in state C (FIG. 3). In state C, the operator informsLNS 202 that autoscrubber 101 is at end of path 300. Path 300 (and inparticular the data associated with each node 302) is saved to memoryaccessible to LNS 202 and stored for future use.

Repeat mode starts in repeat mode initialization state D, where anoperator informs LNS 202 what path 300 to follow (it being appreciatedthat LNS 202 may store (or have access to suitable memory which stores)a library of paths 300). The operator may also position autoscrubber 101on (or near) the selected path 300. In some embodiments, the operatorpositions the autoscrubber 101 at the beginning of path 300. If it isthe case that the operator wishes to start the autoscrubber 101 at anarbitrary location along the path 300, the LNS 202 may, in someembodiments, automatically determine its position along the selectedpath 300 by searching through its node data, or receive an input fromthe operator (through a suitable user interface such as a map), thestarting position of the autoscrubber 101 along the path 300. LNS 202then progresses to state E, where LNS 202 reads in current sensor data(e.g. odometry data, visual data from camera(s) 119, range data fromrange sensors 121 (e.g. LIDAR) and/or the like) and compares the currentsensor data to what it expects to observe at each node 302 along theselected path 300. Using correspondences between the currently observedsensor data and the stored reference sensor data at each node 302 alongthe selected path 300, LNS 202 determines a particular node 302 alongthe selected path 300 (e.g. the node to which autoscrubber 101 is mostproximate) to be its start node 302 and localizes autoscrubber 101relative to this start node 302. In some embodiments, suchcorrespondences are found between visual cues 314 or features identifiedfrom within image data captured by forward facing or upwardly orientedcamera(s) 119. In some embodiments, such correspondences may be foundfrom range cues 316 ascertained by range sensor(s) 121 being matchedwith one or more two-dimensional maps. Some embodiments may combine bothvisual and range cues 314, 316. Visual cues 314 may include, forexample, visually unique tags (which may be distributed in theenvironment to be cleaned) and/or naturally occurring visual features inthe image space corresponding to the environment to be cleaned. Rangecues 316 may include, for example, measurements captured in a singleplane (from a scanning laser or other range sensor(s) 121) and/orarbitrary measurements from sonar or infrared sensors (e.g. point cloudsfrom depth cameras and/or the like).

LNS 202 finds correspondences between the current sensor data and thereference data recorded that it expects to observe in the vicinity ofthe start node 302 and begins to track these correspondences in state E.Depending on the embodiment, the data correspondences may be based onvisual features 314, range cues 316 and/or the like. This localizationstep is shown schematically in FIG. 6A using a single visual cue 314 asan example. As shown in FIG. 6A, autoscrubber 101 is not exactly at thelocation of the start node 302. This can be seen in FIG. 6A by thedifference between the currently observed visual cue 314A and thereference visual cue 314B which corresponds to start node 302.

In some embodiments, such as the illustrated embodiment of FIG. 3, LNS202 may effect a control strategy (based on the difference between thecurrently observed visual cue 314A and the reference visual cue 314Bcorresponding to a start node 302 (i.e. the node at a beginning of asegment 304) to bring autoscrubber 101 to a more precise location ofsuch start node 302. Based on this control strategy, LNS 202 then sendsthe appropriate wheel velocity commands (reference signals 203, 205) tosteering system 100 to effect movement of autoscrubber 101 toward thestart node 302. After identifying the features LNS 202 expects to seeand either guiding autoscrubber 101 back to start node 302 ordetermining that autoscrubber 101 is sufficiently close to start node302, LNS 202 changes the current node from the start node 302 to thenext node 302 along a selected path 300 and advances to state F.

In state F, LNS 202 reads in current sensor data and compares what itcurrently observes to what it expects to observe at the next node 302 inthe selected path 300. This process is shown schematically in FIG. 6B,where a currently observed visual cue 314A is shown as being relativelydistal from the reference visual cue 314B corresponding to the next node302 on the selected path. Based on the correspondences between thecurrently observed visual cue 314A and the reference visual cue 314B atthe next node, LNS 202 determines a suitable control strategy to advanceautoscrubber 101 to the next node 302 on the selected path 300. Based onthis control strategy, LNS 202 then sends the appropriate wheel velocitycommands (reference signals 203, 205) to steering system 100 to effectmovement of autoscrubber 101 toward the next node 302. As autoscrubber101 moves toward the next node 302, the current observed data (e.g.currently observed visual cue 314A) begins to match more closely withthe reference data (e.g. reference visual cue 314B for the next node302), as shown in FIG. 6C. When correspondences between current sensordata (e.g. currently observed visual cue 314A) and reference data (e.g.reference visual cue 314B for the next node 302) is sufficient tosatisfy one or more proximity criteria (as shown in FIG. 6D), LNS 202considers that autoscrubber 101 has reached the next node 302 and LNS202 returns to state E where LNS 202 updates to the next node 302 on theselected path before returning again to state F. If the selected path300 is completed (i.e. autoscrubber reaches the end node 302 of theselected path 300 in state F), LNS 202 advances to state H. In state H,LNS 202 recognizes that it has completed the end of the selected path300 and the navigation operation is terminated.

In some circumstances, the control strategy developed by LNS 202 mayfail (state G). By way of non-limiting example, LNS 202 could enterstate G if LNS 202 determines that, despite movement of autoscrubber 101in accordance with its control strategy, the currently observed data(e.g. visual cue 314A) is not getting closer to the reference data (e.g.visual cue 314B) corresponding to the next node 302. A suitableproximity thresholding inquiry may be used to determine that thenavigation has failed. For example, if, for any group of n controliterations, a distance metric between the currently observed data (e.g.visual cue 314A) and the reference data (e.g. visual cue 314B) is notdecreasing, then LNS 202 may determine that it is in a failure state(state G). Another example of a circumstance in which LNS 202 may enterstate G is where LNS 202 is unable to track visual features 314 and/orrange cues 316, which could be caused by any number of reasons, such asan object occluding the camera(s) 119 or range sensor(s) 121,insufficient lighting to pick out visual features 314 or range cues 316,visual features 314 or range cues 316 being occluded, visual features314 or range cues 316 being removed from the environment and/or thelike.

In state G, LNS 202 may take a number of suitable actions. In someembodiments, LNS 202 may utilize dead reckoning in failure state G basedon odometry data. LNS 202 may operate in this dead reckoning mode untilvisual features 314 or range cues 316 can be found or until a setdistance has been traveled, whichever occurs first. In the event that avisual feature 314 or range cue 316 has been found, LNS 202 may revertback to state E. In the event that a set distance has been travelledusing dead reckoning and no visual features 314 or range cues 316 havebeen found, in some embodiments the LNS 202 may stop the autoscrubber101 and notify the operator. In some embodiments, LNS 202 will causeautoscrubber 101 to stop moving and perhaps to initiate an alarmcommunication to an operator. In some embodiments, LNS 202 may return tostate D from the failure state G to ascertain whether LNS 202 canrecover itself on the selected path 300. In some embodiments, theparticular action(s) taken in failure state G may depend on whether any(or how many) segments 304 along the selected path 300 have beenpreviously navigated and/or whether (or how many times) failure state Ghas been reached during navigation of the selected path.

FIG. 3B depicts a state machine representation of a localization andnavigation system (LNS) suitable for use with the FIG. 1 autoscrubber ina repeat mode according to another particular embodiment. The FIG. 3Brepeat mode starts in state D, which is similar to state D of the FIG. 3repeat mode—LNS 202 obtains from memory a selected path 300 and a map ofreference data associated with the selected path 300. This map ofreference data may include data previously sensed in a teach mode,including, for example, visual features 314, range cues 316 and/or thelike associated with the selected path 300 and each of its nodes 302. Inthis sense, the map contemplated in the FIG. 3B repeat mode is a globalrepresentation of the selected path. The FIG. 3B repeat mode thenprogresses to state I which involves updating the location or pose(location and orientation) of autoscrubber 101 with respect to the mapassociated with the selected path 300 and with respect to the individualnodes 302 on the selected path 300. For the remaining description ofFIG. 3B, the term pose of autoscrubber 101 is used for brevity, but insome embodiments, the location of autoscrubber 101 could be used insteadof its pose.

To estimate the pose of autoscrubber 101 with respect to the mapassociated with the selected path 300, LNS 202 may use current sensordata (e.g. obtained from any of sensors 114, 115, 119, 121 and/or anyother suitable sensors (e.g. other odometry sensors)), a prior pose(which may have been determined in a previous iteration or in the stateD initialization) and the map data ascertained during the teach mode.Based on this data, LNS 202 may localize autoscrubber 101 (e.g.determine the current pose of autoscrubber 101) within the map 300. Onenon-limiting method for localizing autoscrubber within the map of theselected path involves the use of Adaptive Monte Carlo Localization(AMCL). State I may also involve localizing autoscrubber 101 (e.g.determine the current pose of autoscrubber 101) with respect to theindividual nodes 302 on the selected path 300. To estimate the pose ofautoscrubber 101 with respect to the individual nodes 302 associatedwith the selected path, LNS 202 may use current sensor data (e.g.obtained from any of sensors 114, 115, 119, 121 and/or any othersuitable sensors (e.g. other odometry sensors)), a prior pose (which mayhave been determined in a previous iteration or in the state Dinitialization) and the node data ascertained during the teach mode. Thedata associated with each node 302 may comprise pose informationrelative to the map.

The localization procedure with respect to the individual nodes 302 inthe selected path that takes place in state I of the FIG. 3B repeat modemay involve deciding when LNS 202 should start tracking observationsagainst the next node 302 in the selected path 300—i.e. when LNS 202should decide to make the next node 302 in the selected path 300 its“current node” 302. FIGS. 9A and 9B schematically illustrate onetechnique which may be used by LNS 202 for deciding when to starttracking the reference observations from the next node 302 in a selectedpath 300 (i.e. when to update the current node 302) according to aparticular embodiment. In particular, FIGS. 9A and 9B show autoscrubber101, a vector 270 oriented along the selected path 300 between thecurrent node N_(i) and the next node N_(i+1) on the selected path 300, avector 272 between autoscrubber 101 and the current node N_(i) and avector 274 which represents a projection of the vector 272, Projectionvector 274 maintains the orientation of vector 272. FIGS. 9A and 9B alsoshow an angle α between the vectors 270 and 274. LNS 202 may decide toupdate the current node from node N_(i) to node N_(i+1) when the angle αbetween the vectors 270 and 274 is greater than or equal to 90° (i.e.α>=π/2). Accordingly, in the configuration of FIG. 9A, the current nodewould be N_(i), but when autoscrubber 101 reaches the position shown inFIG. 9B, LNS 202 would update the current node to be node N_(i+1). Someembodiments may additionally or alternatively employ a maximumlikelihood filter over all, or a subset, of nodes 302 in the selectedpath 300 to decide which node 302 should be the current node 302 for LNSto track. If there is no next node to track, then the selected path 300is completed, LNS 202 advances to state M. In state M, LNS 202recognizes that it has completed the end of the selected path 300 andthe navigation operation is terminated.

Assuming that there is a next node 302 to track after localization withrespect to the map and with respect to the individual nodes 032 on theselected path 300 is complete in state I (i.e. autoscrubber 101 is notat the end of the path 300), LNS 202 advances to state J. State Jinvolves the use of a control strategy to determine the referencevelocity signals 203, 205 which are used to then control the speeds ofwheels 102, 104 and to steer autoscrubber 101. As discussed above, thesereference velocity signals 203, 205 may be used by controller 116 tocompute control signals 207, 209, 211 (e.g. by one of the controlsystems/algorithms shown in FIG. 10 or 11). The determination of controlsignals 207, 209, 211 may also take place in state J of the FIG. 3Bdepiction. In one particular embodiment, the state J control strategyinvolves the use of two error values: an orientation error (related tothe difference between a current heading or orientation of autoscrubber101 and a desired path heading); and a lateral error (related to thedifference between the current position of autoscrubber 101 projectedonto the selected path 300). Minimizing lateral error attempts to ensureautoscrubber 101 stays on the selected path 300 and minimizingorientation error attempts to ensure autoscrubber 101 is heading in theright direction along the selected path 300. In some embodiments, thestate J control strategy involves implementing an angular velocitycontrol signal for an angular velocity about a vertical axis bycombining the values from the two sources of error and constructing,from this combined error, an angular velocity control signal. In someembodiments, the state J control strategy involves allowing the forwardvelocity (e.g. the velocity implemented by positive torque mechanism106) to remain constant. The angular velocity control signal (determinedfrom the combined error using a PID control scheme) may then be mappedto wheel velocity reference signals 203, 205 based on a kinematic modelof autoscrubber 101. As will be understood to those skilled in the art,this kinematic model may be based on the geometry of autoscrubber 101,characteristics of the wheels 102, 104, the steering torque mechanisms108, 109 and the like.

Some embodiments of the state J control strategy implementation mayinvolve incorporating additional information about the curvature of theselected path 300 (e.g. in addition to the orientation error and lateralerror). Adding a dependency on the control strategy on the curvature ofthe selected path 300 may help to anticipate turns and may thereby helpto reduce over/under steering. The use of such curvature informationinvolves the determination of curvature either a priori or at run time.In some embodiments, this control signal B may be determined accordingto:

$\begin{matrix}{B = {{k_{1}L\frac{\sin(a)}{a}} + {k_{2}{\mspace{11mu}\;}a\mspace{14mu}{{sign}(v)}} + {k_{3}\left( \frac{c\mspace{14mu}{\cos(a)}}{\left( {1 - {Lc}} \right)} \right)}}} & (4)\end{matrix}$and then scaling the control signal B by the forward velocity to arriveat the angular velocity control signal w according to:w=Bv  (5)where w is the angular velocity control signal, v is the forwardvelocity, L is the lateral error, a is the orientation error, c is thecurvature term, and k₁ k₂, k₃ are configurable gains,

Autoscrubber 101 will typically have kinematic constraints. Exemplaryconstraints may include minimum/maximum velocities for wheels 102, 104,left and right wheels 102, 104 cannot rotate in different angulardirections, the angular velocities of left and right wheels 102, 104must be greater than zero and/or the like. Such constraints can be addedto the state J control strategy by checking if a constraint would beviolated and then scaling the output command (angular velocity w) suchthat the constraint is satisfied. For example, accommodating suchconstraints may involve:w=YBv  (6)Y=min{1,p _(i)} for all i|p _(i)>0  (7)where Y is a further scaling factor and p_(i) is a constraint of theform:

$\begin{matrix}{p_{i} = \frac{\left( {{velocity}\mspace{14mu}{constraint}} \right)}{\left( {{control}\mspace{14mu}{value}} \right)}} & (8)\end{matrix}$and “control value” is w prior to multiplication by the scaling factorY.

In some circumstances, a path 300 determined during teach mode is noisyor jittery (eg. non-smooth). Such noisy paths may producecorrespondingly noisy orientation and lateral error measurements andcurvature estimates during autonomous navigation. To assist LNS 202,some embodiments may involve smoothing the points that make up the paths300 learned in teach mode, which ultimately results in a smoothercontrol signal w and correspondingly smoother velocity reference values203, 205. One technique to smooth a path 300 is to compute the weightedmean for each (x, y) position in the path based on a set of neighboringpoints (e.g. points within some threshold distance of a given point).The performance of this technique is subject to the variance of noiseand distribution of points. Another technique to smooth a path 300involves the use of a non-parametric regression method, such as locallyweighted scatterplot smoothing (LOESS), and fitting a polynomial to thepath. By independently fitting polynomials to the X positions and Ypositions of the path a smooth function can be produced over the entirepath. This has the nice property of having continuous derivatives, whichis useful for curvature approximation for the robot controller.

As discussed above, the angular velocity control signal w determined instate J may then be mapped to wheel velocity reference signals 203, 205based on a kinematic model of autoscrubber 101. State J may then involveusing wheel velocity reference signals 203, 205 to determine suitablecontrol signals 207, 209, 211 for steering torque mechanisms 108, 109and for positive torque mechanism 106. LNS may then return to state I.

If there is an obstacle detected on the selected path 300 ahead ofautoscrubber 101 (e.g. by camera(s) 119 and/or range finding sensor(s)121), LNS 202 enters state K. Any of a variety of obstacle avoidancestrategies could be executed in state K. Non-limiting examples of suchobstacle avoidance techniques include planning detours (modified paths300) around the obstacles. LNS 202 may apply heuristics, such as waitingfor an obstacle to move before planning a modified path 300 and may onlyplan modified paths 300 in “safe” zones around the selected path 300. Anexample of a “safe” zone may be all locations in the map of the worldwhere autoscrubber 101 has traversed previously (either during teach orrepeat). If state K provides a modified path 300, one that is notobstructed by obstacle(s), LNS may return to state J, which implements acontrol strategy relative to the modified path 300.

Referring to FIG. 3B, if there is a problem with localization in stateI, LNS 202 may enter state L, where LNS 202 may attempt to recover itslocalization. Any of a number of recovery methods could be executed instate L. For example, LNS may cause autoscrubber 101 to stop moving,notify the user, and wait. An additional or alternative method maycomprise executing a global re-localization using Adaptive Monte CarloLocalization (AMCL). If the state L re-localization is successful, LNS202 may return to state I. LNS 202 may determine (e.g. in state I) thatit has reached the end node 302 of the selected path 300, or within somethreshold value of the end node 302, in which case LNS 202 may enterstate M. In state M, LNS 202 causes autoscrubber 101 to stop moving andmay notify the operator. LNS 202 may also cause autoscrubber 101 toexecute some end of path behavior—e.g. return to a particular (home)location or the like.

FIG. 4 is a schematic depiction of a modular software architecture forLNS 202 according to a particular embodiment. LNS 202 has twooperational modes (teach and repeat) as described above. The FIG. 4schematic depiction shows LNS 202 divided into these operational modes,although it will be appreciated that in practice some modules maycomprise the same or similar components (e.g. hardware and/or softwarecomponents). Data gatherer 320 collects data from sensors 114, 115, 119,121 and sensor filters and saves the data in persistent storage 321(shown as raw data in FIG. 4). Teacher component 322 processes thestored data 321 into paths 300, which comprise nodes 302, as discussedabove. Path handler (which may be implemented in the form of a pathserver) 324 saves and loads paths 300 into persistent storage (notshown) accessible to LNS 202. Optionally, data gatherer 320 may bebypassed and teacher component 322 can process the live data directlyfrom sensors 114, 115, 119, 121. In repeat module, path localizer 326processes data received from sensors 114, 115, 119, 121 and a selectedpath 300 as input to determine where autoscrubber 101 is locatedrelative to its next objective.

Kinematic planner 328 may enforce constraints (e.g. kinematicconstraints of autoscrubber 101 and/or obstacles on the selected path300) on LNS 202. Kinematic planner 328 may have some “hard-programmed”constraints. Examples of such hard-programmed constraints include:maximum acceleration and deceleration of autoscrubber 101, maximum speedof autoscrubber 101, minimum turning radius of autoscrubber 101, wheels102, 104 cannot rotate backwards, and/or the like. Using theseconstraints, kinematic planner 328 prevents LNS 202 from sending wheelvelocity commands that the physical system (autoscrubber 101) cannotachieve. In addition to hard-programmed constraints, kinematic planner328 may also take obstacles into account and may cause LNS 202 to takevarious alternative strategies in the face of such obstacles. Kinematicplanner 328 may compute and pass left and right wheel referencevelocities 203, 205 to motor controller 330 so that motor controller 330may execute the kinematically constrained wheel commands.

FIG. 4B is a schematic depiction of a modular software architecture 202Bfor LNS 202 according to another particular embodiment. For the mostpart, the FIG. 4B software architecture 202B is substantially similar tothe FIG. 4 software architecture described above and components havingsimilar functionality are annotated in FIG. 4B using similar referencenumerals. The FIG. 4B software architecture 202B differs from that ofFIG. 4 in that FIG. 4B expressly shows sensor filters 342, storage 344and user interface 714B (which are present in the FIG. 4 architecture,but omitted for brevity). The FIG. 4B software architecture 202B differsfrom that of FIG. 4 in that the FIG. 4B architecture 202B comprisesglobal planner 340. Global planner 340 takes as input the path 300 frompath server 324 and the current estimated pose with respect to the path300 from the localizer component 326. Global planner 340 outputs asubset of the entire path 300 and a relative pose for the kinematicplanner 328 to process. In some embodiments, global planner 340 may alsoperform obstacles avoidance by detecting potential obstacles blockingthe desired path for autoscrubber 101 and planning detours around theobstacles. Global planner 340 may apply heuristics such as waiting foran obstacle to move before planning a detour and only plan detours in“safe” zones around the path 300. An example of a “safe” zone may be alllocations in the map of the world where autoscrubber 101 has traversedpreviously (either during teach or repeat).

While a number of exemplary aspects and embodiments are discussedherein, those of skill in the art will recognize certain modifications,permutations, additions, and sub-combinations thereof. For example:

-   -   In the illustrated embodiment described above, autoscrubber 100        comprises a pair of drive wheels 102, 104. In some embodiments,        autoscrubber 100 may comprise more than two drive wheels. In        some embodiments, in addition to its drive wheels, autoscrubber        100 may comprise any suitable number of idler wheels. Such idler        wheels may rotate independently. In some embodiments, such idler        wheels are mounted using castor mountings or the like which        facilitate pivotal movement of the horizontal idler wheel axes        (e.g. the axes about which the idler wheels rotate) about        generally vertically oriented axes.    -   The embodiments described for the most part herein are described        in connection with autoscrubbers. In some embodiments, the any        of the technology described herein can be used for other robotic        vehicle apparatus capable of operating in a manual mode wherein        an operator steers the robotic vehicle apparatus and an        autonomous mode wherein the robotic vehicle apparatus steers        itself independently of the operator.    -   In the embodiments described for the most part herein, when the        autoscrubber is in a manual operational mode, the operator        steers the autoscrubber by directly applying force to a handle        or the like which is physically connected to the autoscrubber        and to transfer lateral force to the autoscrubber which may in        turn result in the drive wheels rotating with different angular        velocities. In some embodiments, autoscrubbers may comprise more        complex manual mode steering mechanisms. Some such manual mode        steering mechanisms be used by an operator to change the        orientation of drive wheels or to exert lateral force to the        drive wheels. Some such manual mode steering mechanisms be used        by an operator to provide different left and right drive torques        to the left and right drive wheels. In some embodiments, an        operator may be present in a vicinity of the autoscrubber when        operating the autoscrubber in manual mode. For example, an        operator may be present at the autoscrubber to push on the        handle or may ride on the autoscrubber and exert force on the        steering mechanism. This is not necessary. In some embodiments        the operator may control the autoscrubber in manual operational        mode using a remote user interface—e.g. remote user interfaces        252, 254 shown in FIG. 8.        -   In some embodiments, two motors may be used in a            differential configuration to implement both forward            movement and steering. An example of such an embodiment is            shown in FIG. 12, which shows an autoscrubber 500 having a            combined steering and drive system 501 comprising two            independently controllable drive and steering torque            mechanisms 508, 509—comprising corresponding motors 508A,            509A suitable connected to independently drive wheels 502,            504. A controller 516 may be used to supply control signals            to drive and steering torque mechanisms 508, 509 to            independently control the rotational velocities of wheels            502, 504 based on feedback from rotational sensors 514, 515.            In many respects, operation of autoscrubber 500 may be            similar to that of autoscrubber 101 described herein, except            that, in autonomous operational mode, the determination of            positive torque and steering torque may be combined in a            closed loop control mechanism. In manual operational mode,            controller may implement a “freewheeling” control strategy            to permit wheels 502, 504 to “freewheel” (in a manner            similar to the freewheeling techniques described above) in a            suitable region around some positive torque offset. For            example, if an operator sets a forward velocity to be x,            then controller 516 may implement a freewheeling technique            in a region around this velocity x, so that the operator has            an experience where the operator is not caused to do extra            work to turn autoscrubber 500 by causing a velocity that is            in a region around x. For example, rotational sensors could            be configured to measure angular velocities of the left and            right drive wheels and to provide these measurements to the            controller. While operating in the manual operational mode,            an operator may set nominal left and right positive drive            signals for torque mechanisms 508, 509 (and corresponding            nominal angular velocities for wheels 502, 504) via a user            interface, but the operator may then steer the apparatus so            that drive wheels 502, 504 have actual angular velocities            that are different than their nominal angular velocities.            Controller 516 may be configured to determine left and right            freewheeling adjustments and to apply the left and right            freewheeling adjustments to the nominal left and right            positive drive signals to obtain resultant left and right            positive drive signals. When these resultant drive signals            are applied to left and right torque mechanisms 508, 509,            these resultant drive signals cause the positive torque            mechanisms 508, 509 to rotate wheels 502, 504 with the            actual angular velocities which simulate a freewheeling            effect that minimizes the need to apply differential torque            to drive wheels 502, 504 to cause them to rotate at angular            velocities other than the nominal angular velocities. This            freewheeling methodology may simulate the transaxle of            conventional autoscrubbers.    -   In some embodiments, the steering system does not require        steering torque mechanisms 108, 109. Some such embodiments may        instead comprise another steering wheel or wheels (not shown) at        some suitable distance behind or in front of the drive axle of        drive wheels 102, 104. Example embodiments of such a system may        comprise any one or more of:        -   One or more steering wheel(s) (caster-mounted or otherwise)            which may replace existing caster wheels or which may be            additions to existing caster wheels. Such one or more            steering wheel(s) can be controllably and actively steered            by a suitable steering mechanism to control the orientation            of the steering wheel(s) and the corresponding direction of            the autoscrubber 101. Such steering wheel(s) may be powered            (in the sense that they also act like drive wheels) or            unpowered.        -   One or more omniwheel(s) mounted perpendicular to drive            wheels 102, 104 at some distance behind (or in front of) the            drive axle of drive wheels 102, 104, which can be driven in            either transverse direction to change the direction of            autoscrubber 101, but which do not provide substantial            resistance to forward or backward movement.    -   In any such embodiments incorporating steering wheels, the        steering wheel(s) may be configured to permit free rotation        (e.g. “freewheeling”) either via mechanical disconnection of the        wheel or using a freewheeling control mechanism of the type        described herein.

What is claimed is:
 1. A robotic vehicle apparatus operable in a manualmode wherein an operator steers the robotic vehicle apparatus and anautonomous mode wherein the robotic vehicle apparatus steers itselfindependently of the operator, the robotic vehicle apparatus comprising:a chassis supporting a left drive wheel and a right drive wheel forrotation with respect to the chassis; a positive torque mechanismmounted to the chassis and connected to provide left positive drivingtorque to the left drive wheel and to provide right positive drivingtorque to the right drive wheel to thereby move the apparatus; and asteering system embodied separately from the positive torque mechanism,the steering system mounted to the chassis for steering the apparatuswhen the apparatus is in an autonomous operational mode, the steeringsystem comprising: a left steering torque mechanism connectable to applyleft steering torque to the left drive wheel independently of the rightdrive wheel; a right steering torque mechanism connectable to applyright steering torque to the right drive wheel independently of the leftdrive wheel; and a controller connectable to provide a positive torquedrive signal to the positive torque mechanism, a left steering torquesignal to the left steering torque mechanism and a right steering torquesignal to the right steering torque mechanism when the apparatus is inthe autonomous operational mode and configured to controllably steermovement of the apparatus when the apparatus is in an autonomousoperational mode by determining the left steering torque signal and theright steering torque signal and providing these left and right steeringtorque signals to the left and right steering torque mechanisms.
 2. Arobotic vehicle apparatus according to claim 1 wherein a single positivetorque motor is connected to a transaxle which is in turn connected tothe left and right drive wheels to thereby split the positive drivingtorque between the left drive wheel and the right drive wheel.
 3. Arobotic vehicle apparatus according to claim 1 wherein the positivetorque mechanism comprises a left positive torque motor connected toprovide the left positive driving torque to the left drive wheel and aright positive torque motor connected to provide the right positivedriving torque to the right drive wheel.
 4. A robotic vehicle apparatusaccording to claim 1 wherein the left steering torque mechanismcomprises a left negative steering torque mechanism which is connectableto apply left negative steering torque to the left drive wheel, the leftnegative steering torque acting to decelerate any rotation of the leftdrive wheel with respect to the chassis and wherein the right steeringtorque mechanism comprises a right negative steering torque mechanismwhich is connectable to apply right negative steering torque to theright drive wheel, the right negative steering torque acting todecelerate any rotation of the right drive wheel with respect to thechassis.
 5. A robotic vehicle apparatus according to claim 4 wherein thecontroller is configured to steer the apparatus when the apparatus is inthe autonomous operational mode by determining the left and rightsteering torque signals to be different from one another and byproviding these different left and right steering torque signals to theleft and right negative steering torque mechanisms to thereby cause theleft and right negative steering torque mechanisms to apply differentamounts of left negative steering torque to the left drive wheel andright negative steering torque to the right drive wheel.
 6. A roboticvehicle apparatus according to claim 4 wherein the left and rightsteering torque mechanisms respectively comprises left and rightsteering motors which are mechanically connectable to the left and rightdrive wheels.
 7. A robotic vehicle apparatus according to claim 6wherein the left steering motor is mechanically connectable to the leftdrive wheel by a left braking mechanism which is connectable to the leftdrive wheel when the apparatus is in the autonomous operational mode andwhich is mechanically disconnected from applying left negative steeringtorque to the left drive wheel when the apparatus is in the manualoperational mode and the right steering motor is mechanicallyconnectable to the right drive wheel by a right braking mechanism whichis connectable to the right drive wheel when the apparatus is in theautonomous operational mode and which is mechanically disconnected fromapplying right negative steering torque to the right drive wheel whenthe apparatus is in the manual operational mode.
 8. A robotic vehicleapparatus according to claim 6 wherein the left steering motor ismechanically connectable to the left drive wheel by a left steeringmechanism comprising a left runner wheel which is connectable to theleft drive wheel by friction to cause the left runner wheel to rotatewith the left drive wheel when the apparatus is in the autonomousoperational mode and the right steering motor is mechanicallyconnectable to the right drive wheel by a right steering mechanismcomprising a right runner wheel which is connectable to the right drivewheel by friction to cause the right runner wheel to rotate with theright drive when the apparatus is in the autonomous operational mode. 9.A robotic vehicle apparatus according to claim 8 wherein application ofleft and right negative steering torque to the left and right drivewheels rotates the left and right steering motors through the frictionconnection of the left and right runner wheels to the left and rightdrive wheels, and rotation of the left and right steering motorsgenerates energy, the generated energy connectable to a charge storagedevice.
 10. A robotic vehicle apparatus according to claim 6 wherein theleft steering motor is mechanically connectable to the left drive wheelby a left steering mechanism comprising a left chain mechanism and theright steering motor is mechanically connectable to the right drivewheel by a right steering mechanism comprising a right chain mechanism.11. A robotic vehicle apparatus according to claim 1 wherein the leftsteering torque mechanism is configurable, by positive and negative leftsteering torque signals, to apply: left positive steering torque to theleft drive wheel, the left positive steering torque acting to accelerateany rotation of the left drive wheel with respect to the chassis; andleft negative steering torque to the left drive wheel, the left negativesteering torque acting to decelerate any rotation of the left drivewheel with respect to the chassis and wherein the right steering torquemechanism is configurable, by positive and negative right steeringtorque signals, to apply: right positive steering torque to the rightdrive wheel, the right positive steering torque acting to accelerate anyrotation of the right drive wheel with respect to the chassis; and rightnegative steering torque to the right drive wheel, the right negativesteering torque acting to decelerate any rotation of the right drivewheel with respect to the chassis.
 12. A robotic vehicle apparatusaccording to claim 11 wherein the controller is configured to steer theapparatus when the apparatus is in the autonomous operational mode bydetermining the left and right steering torque signals to be differentfrom one another and by providing these different left and rightsteering torque signals to the left and right steering torque mechanismsto thereby cause the left and right steering torque mechanisms to applydifferent amounts of left steering torque to the left drive wheel andright steering torque to the right drive wheel.
 13. A robotic vehicleapparatus according to claim 11 wherein the left and right steeringtorque mechanisms respectively comprise left and right steering motorswhich are mechanically connectable to the left and right drive wheels.14. A robotic vehicle apparatus according to claim 13 wherein the leftsteering motor is mechanically connectable to the left drive wheel by aleft steering mechanism comprising a left runner wheel which isconnectable to the left drive wheel by friction to cause the left runnerwheel to rotate with the left drive wheel when the apparatus is in theautonomous operational mode and the right steering motor is mechanicallyconnectable to the right drive wheel by a right steering mechanismcomprising a right runner wheel which is connectable to the right drivewheel by friction to cause the right runner wheel to rotate with theright drive wheel when the apparatus is in the autonomous operationalmode.
 15. A robotic vehicle apparatus according to claim 1 wherein theleft steering torque mechanism comprises a left positive steering torquemechanism which is connectable to apply left positive steering torque tothe left drive wheel, the left positive steering torque acting toaccelerate any rotation of the left drive wheel with respect to thechassis.
 16. A robotic vehicle apparatus according to claim 1 comprisinga user interface and wherein, in the manual operational mode, anoperator controls the left positive driving torque applied to the leftdrive wheel and the right positive driving torque applied to the rightdrive wheel via left and right positive drive commands configurable bythe user interface.
 17. A robotic vehicle apparatus according to claim16 wherein the controller is configured to receive the left and rightpositive drive commands and to provide one or more correspondingpositive driving torque signals to the positive torque mechanism tocause the positive torque mechanism to provide the left and rightpositive driving torques to the left and right drive wheels and whereinthe controller is configured to determine the one or more correspondingpositive driving torque signals in an open loop manner.
 18. A roboticvehicle apparatus according to claim 1 comprising a handle for steeringthe apparatus when the apparatus is in the manual operational mode, thehandle connected to the chassis and shaped to be grippable by anoperator to steer the movement of the apparatus when the apparatus is inthe manual operational mode via application of force to the handle. 19.A robotic vehicle apparatus according to claim 1 comprising a manualmode steering mechanism which is manipulable by the operator when theapparatus is in the manual operational mode to exert lateral force onthe left and right drive wheels and to thereby change their orientationswith respect to the chassis.
 20. A robotic vehicle apparatus accordingto claim 1 comprising a manual mode steering mechanism which ismanipulable by the operator when the apparatus is in the manualoperational mode to cause the positive torque mechanism to providedifferent left and right drive torques to the left and right drivewheels.
 21. A robotic vehicle apparatus according to claim 1 comprisingone or more range sensors mounted to the chassis for capturing rangeinformation in relation to objects in the environment in which theapparatus operates and wherein the controller is configured to operatein a teach mode and a repeat mode wherein: during the teach mode, theapparatus is in the manual operational mode and the one or more rangesensors capture and store range cues at each of the plurality of nodesalong a path during movement of the apparatus along the path; and duringthe repeat mode, the apparatus is in the autonomous operational mode,the one or more range sensors capture range data to provide range datafeedback and the controller is configured to determine one or more ofthe positive torque drive signal, the left steering torque drive signaland the steering right torque drive signal, based at least in part on acomparison of the range data feedback and at least some of the rangecues captured and stored at each of the plurality of nodes during theteach mode.
 22. A robotic vehicle apparatus according to claim 21wherein, during the repeat mode, the controller is configured todetermine one or more of the positive torque drive signal, the leftsteering torque drive signal and the right steering torque drive signal,based at least in part on a comparison of the range data feedback andthe range cues captured and stored for a current one of the plurality ofnodes during the teach mode and wherein the current node is updated asthe apparatus traverses the path.
 23. A robotic vehicle apparatusaccording to claim 21 wherein, during the repeat mode, the controller isconfigured to determine one or more of the positive torque drive signal,the left steering torque drive signal and the right steering torquedrive signal, based at least in part on a comparison of the range datafeedback and the range cues captured and stored for a subset pluralityof the plurality of nodes during the teach mode, the subset plurality ofnodes corresponding to a threshold vicinity of a current location of theapparatus and the subset plurality updated as the apparatus traversesthe path.
 24. A robotic vehicle apparatus according to claim 21 wherein,during the repeat mode, the controller is configured to determine one ormore of the positive torque drive signal, the left steering torque drivesignal and the right steering torque drive signal, based at least inpart on a comparison of the range data feedback and a map incorporatingthe range cues captured and stored for all of the plurality of nodesduring the teach mode.
 25. A robotic vehicle apparatus according toclaim 1 comprising one or more odometry sensors and wherein thecontroller is configured to operate in a teach mode and a repeat modewherein: during the teach mode, the apparatus is in the manualoperational mode and the one or more odometry sensors capture and storereference odometry data at each of the plurality of nodes along a pathduring movement of the apparatus along the path; and during the repeatmode, the apparatus is in the autonomous operational mode, the one ormore odometry sensors capture odometry data to provide odometry datafeedback and the controller is configured to determine one or more ofthe positive torque drive signal, the left steering torque drive signaland the right steering torque drive signal, based at least in part on acomparison of the odometry data feedback and at least some of thereference odometry data captured and stored at each of the plurality ofnodes during the teach mode.
 26. A robotic vehicle apparatus operable ina manual mode wherein an operator steers the robotic vehicle apparatusand an autonomous mode wherein the robotic vehicle apparatus steersitself independently of the operator, the robotic vehicle apparatuscomprising: a chassis supporting a left drive wheel and a right drivewheel for rotation with respect to the chassis; a positive torquemechanism mounted to the chassis and connected to provide left positivedriving torque to the left drive wheel and to provide right positivedriving torque to the right drive wheel to thereby move the apparatus,wherein the positive torque mechanism comprises a left positive torquemotor connected to provide the left positive driving torque to the leftdrive wheel and a right positive torque motor connected to provide theright positive driving torque to the right drive wheel; a steeringsystem mounted to the chassis for steering the apparatus when theapparatus is in an autonomous operational mode, the steering systemcomprising: a left steering torque mechanism connectable to apply leftsteering torque to the left drive wheel independently of the right drivewheel; a right steering torque mechanism connectable to apply rightsteering torque to the right drive wheel independently of the left drivewheel; a controller connectable to provide a left steering torque signalto the left steering torque mechanism and a right steering torque signalto the right steering torque mechanism when the apparatus is in theautonomous operational mode and configured to controllably steermovement of the apparatus when the apparatus is in an autonomousoperational mode by determining the left steering torque signal and theright steering torque signal and providing these left and right steeringtorque signals to the left and right steering torque mechanisms; andleft and right sensors connected to measure parameters indicative ofangular velocities of the left and right drive wheels and to providethese measurements to the controller, wherein, when operating in themanual operational mode: an operator sets nominal left and rightpositive drive signals to the left and right positive torque motors viaa user interface, the nominal left and right positive drive signalscorresponding to nominal angular velocities of the left and right drivewheels, and then steers the apparatus so that the left and right drivewheels have actual left and right angular velocities that are differentthan the nominal angular velocities; and the controller is configured todetermine left and right freewheeling adjustments and to apply the leftand right freewheeling adjustments to the nominal left and rightpositive drive signals to obtain resultant left and right positive drivesignals which, when applied to left and right positive torque motors,cause the left and right drive wheels to rotate with the actual left andright angular velocities to thereby simulate a freewheeling effect whichminimizes the need to apply differential torque to the left and rightdrive wheels to cause them to rotate at angular velocities other thanthe nominal angular velocities.
 27. A robotic vehicle apparatus operablein a manual mode wherein an operator steers the robotic vehicleapparatus and an autonomous mode wherein the robotic vehicle apparatussteers itself independently of the operator, the robotic vehicleapparatus comprising: a chassis supporting a left drive wheel and aright drive wheel for rotation with respect to the chassis; a positivetorque mechanism mounted to the chassis and connected to provide leftpositive driving torque to the left drive wheel and to provide rightpositive driving torque to the right drive wheel to thereby move theapparatus; a steering system mounted to the chassis for steering theapparatus when the apparatus is in an autonomous operational mode, thesteering system comprising: a left steering torque mechanism connectableto apply left steering torque to the left drive wheel independently ofthe right drive wheel; a right steering torque mechanism connectable toapply right steering torque to the right drive wheel independently ofthe left drive wheel; a controller connectable to provide a leftsteering torque signal to the left steering torque mechanism and a rightsteering torque signal to the right steering torque mechanism when theapparatus is in the autonomous operational mode and configured tocontrollably steer movement of the apparatus when the apparatus is in anautonomous operational mode by determining the left steering torquesignal and the right steering torque signal and providing these left andright steering torque signals to the left and right steering torquemechanisms; and one or more cameras mounted to the chassis for capturingimages of an environment in which the apparatus operates wherein atleast one of the one or more cameras is mounted to the chassis such thatits field of view is oriented primarily upwardly for capturing images ofa ceiling of the environment in which the apparatus operates; and one ormore range sensors mounted to the chassis for capturing rangeinformation in relation to objects in the environment in which theapparatus operates.
 28. A robotic vehicle apparatus operable in a manualmode wherein an operator steers the robotic vehicle apparatus and anautonomous mode wherein the robotic vehicle apparatus steers itselfindependently of the operator, the robotic vehicle apparatus comprising:a chassis supporting a left drive wheel and a right drive wheel forrotation with respect to the chassis; a positive torque mechanismmounted to the chassis and connected to provide left positive drivingtorque to the left drive wheel and to provide right positive drivingtorque to the right drive wheel to thereby move the apparatus; asteering system mounted to the chassis for steering the apparatus whenthe apparatus is in an autonomous operational mode, the steering systemcomprising: a left steering torque mechanism connectable to apply leftsteering torque to the left drive wheel independently of the right drivewheel; a right steering torque mechanism connectable to apply rightsteering torque to the right drive wheel independently of the left drivewheel; a controller connectable to provide a left steering torque signalto the left steering torque mechanism and a right steering torque signalto the right steering torque mechanism when the apparatus is in theautonomous operational mode and configured to controllably steermovement of the apparatus when the apparatus is in an autonomousoperational mode by determining the left steering torque signal and theright steering torque signal and providing these left and right steeringtorque signals to the left and right steering torque mechanisms; and oneor more cameras mounted to the chassis for capturing images of anenvironment in which the apparatus operates, and wherein the controlleris configured to operate in a teach mode and a repeat mode wherein:during the teach mode, the apparatus is in the manual operational modeand the one or more cameras capture and store image data at each of aplurality of nodes along a path during movement of the apparatus alongthe path; and during the repeat mode, the apparatus is in the autonomousoperational mode, the one or more cameras capture image data to provideimage data feedback and the controller is configured to determine one ormore of a positive torque drive signal applied to the positive torquemechanism, the left steering torque drive signal and the right steeringtorque drive signal, based at least in part on a comparison of the imagedata feedback and at least some of the image data captured and stored ateach of the plurality of nodes during the teach mode.
 29. A roboticvehicle apparatus according to claim 28 wherein, during the repeat mode,the controller is configured to determine one or more of the positivetorque drive signal, the left steering torque drive signal and the rightsteering torque drive signal, based at least in part on a comparison ofthe image data feedback and the image data captured and stored for acurrent one of the plurality of nodes during the teach mode and whereinthe current node is updated as the apparatus traverses the path.
 30. Arobotic vehicle apparatus according to claim 28 wherein, during therepeat mode, the controller is configured to determine one or more ofthe positive torque drive signal, the left steering torque drive signaland the right steering torque drive signal, based at least in part on acomparison of the image data feedback and the image data captured andstored for a subset plurality of the plurality of nodes during the teachmode, the subset plurality of nodes corresponding to a thresholdvicinity of a current location of the apparatus and the subset pluralityupdated as the apparatus traverses the path.
 31. A robotic vehicleapparatus according to claim 28 wherein, during the repeat mode, thecontroller is configured to determine one or more of the positive torquedrive signal, the left steering torque drive signal and the rightsteering torque drive signal, based at least in part on a comparison ofthe image data feedback and a map incorporating the image data capturedand stored for all of the plurality of nodes during the teach mode. 32.A method for moving a robotic vehicle apparatus that is operable in amanual mode wherein an operator steers the robotic vehicle apparatus andan autonomous mode wherein the robotic vehicle apparatus steers itselfindependently of the operator, the method comprising: providing arobotic vehicle apparatus comprising: a chassis supporting a left drivewheel and a right drive wheel for rotation with respect to the chassis;a positive torque mechanism connected to provide left positive drivingtorque to the left drive wheel and to provide right positive drivingtorque to the right drive wheel to thereby move the apparatus; asteering system embodied separately from the positive torque mechanism,the steering system mounted to the chassis for steering the apparatuswhen the apparatus is in an autonomous operational mode, the steeringsystem comprising: a left steering torque mechanism connectable to applyleft steering torque to the left drive wheel independently of the rightdrive wheel and a right steering torque mechanism connectable to applyright steering torque to the right drive wheel independently of the leftdrive wheel; and when the apparatus is in the autonomous operationalmode: determining, by a controller, a positive torque drive signal, aleft steering torque signal and a right torque drive signal; andproviding the positive torque drive signal to the positive torquemechanism, the left steering torque signal and the right torque drivesignal to the left and right steering torque mechanisms to therebycontrollably steer the apparatus by effecting different left and rightangular velocities for the left and right drive wheels.